speed up traj_from_mdraj (don't recalc unitcells)
speed up traj_from_mdraj (don't recalc unitcells)

openpathsampling/openpathsampling,dwhswenson/openpathsampling,dwhswenson/openpathsampling,openpathsampling/openpathsampling,dwhswenson/openpathsampling,choderalab/openpathsampling,choderalab/openpathsampling,openpathsampling/openpathsampling,choderalab/openpathsampling,dwhswenson/openpathsampling,openpathsampling/openpathsampling